Interspecific competition and other factors influencing the performance of Douglas-fir saplings in the Oregon Coast Range

Abstract

Regression models describing total height, stem diameter, stem volume index, and crown volume index of individual 4- to 9-year-old saplings of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) were developed from a retrospective analysis of two site-preparation experiments. The models, which accounted for between 64 and 73% of the variation in individual tree size, integrate environmental and morphological factors that can influence the performance of Douglas-fir saplings into one set of equations. Interspecific competition and amount of animal damage were negatively correlated with tree size. Tree age, 1st-year height, and the use of prescribed burning were positively correlated with tree size. When factors were held constant, trees were largest on steep southeast slopes. The models indicated that tree age, competing vegetation, animal damage, and initial seedling size had a dominant influence on the performance of Douglas-fir saplings, while prescribed burning and topography were of relatively minor importance.